TODO: A way to see the path of the currently selected item in any grouplike
      element. Each item in the path should be a button that, when pressed,
      makes the MAIN grouplike view navigate there.
      (Done!)

TODO: A "shuffle queue" button!
      (Half-way done -- the functionality is there, press "S", but there's no
      button for it yet.)

TODO: A "clear queue" button.

TODO: A way to jump to an item with a particular name. Probably press "/".
      It'd be nice if the closest match got highlighted while you were typing.
      (Done!)

TODO: "Queue to play next"... maybe also a cursor in the queue list, which
      would tell after what track to place newly-queued items?
      (Done!)

TODO: Scroll to the selected track once it starts playing when selected from
      the queue.

TODO: process.on('SIGWINCH', () => ...) -- detect terminal resize!!
      (Done!)

TODO: Pressing enter in the queue seems to not be doing the right thing?
      It should NOT move the selected item anywhere in the queue; it should
      just select and play that track.
      (Done!)

TODO: iTunes downloader - test this.

TODO: Warn if no mkfifo (means controls won't work).

TODO: file:// support for crawl-local.
      (Done!)

TODO: Pass YouTube playlist or http://.../playlist.json-like URLs to use them
      as playlists (crawl automatically).
      (Done!)

TODO: There's some weird glitch where, if downloaderArg is missing (=== ""),
      it'll play.. something by Jake Chudnow?? -- Okay, looks like it's using
      ~/.mtui/downloads/<locallink, etc>/ as the directory for where it would
      put the download file (because it's .../localink/ + encode(dlArg) and
      dlArg is empty). The way the cache works is that it checks if there is
      already a file in that directory, and there IS: a directory for another
      track download! But the cache doesn't know this; it just thinks that
      directory is the MP3 file (or whatever). So it returns it. MPV works fine
      if you pass it a directory that contains music files, so in my case,
      72_food (by Jake Chudnow) plays. (That's the first thing returned by
      readdir, I suppose.)
      (Done!)

TODO: Mouse support, obviously.

TODO: Ctrl-O'ing a playlist sets the left-pane's selected index to the second
      item, for some reason. (Regardless of what you had selected before..)

TODO: "Open in new tab" in the Open prompt.

TODO: Inspect the inevitable memory issues that are absolutely 100% sure to
      become a problem with opening playlists on the fly.

TODO: Cancelling the "enter a playlist source" dialog shouldn't also stop the
      current song.
      (Done!)

TODO: Move TabberElement to tui-lib, at some point.

TODO: Make PathElements selectable (again).
      (Done!)

TODO: Make the tabber UI show handy information, like what tab you've got
      selected, how many tabs there are, the usual (same way a browser tabber
      works).
      (Done!)

TODO: A "bookmarked playlists" list in the UI, so you can quickly load up
      playlists you often use. (Let anything go here, like YT playlist URLs,
      file paths, etc.)

TODO: Get rid of "WARNING: unable to extract uploader nickname", which comes
      from youtube-dl.
      (Done!)

TODO: Fix crashes related to the window resizing while a download is occurring
      (i.e. the braille "download spinner" is showing). Very weird!

TODO: Investigate performance issues with very very long ListScrollForms.
      (Done!)

TODO: At some point, putting mtui downloads in ~/.mtui - but preferrably with
      a more humanish structure - would be quite nice..!

TODO: Press "M" to show a context menu. (Done!)

TODO: Figure out a keybinding for Mark (in edit mode) - probably Ctrl-M.
      (I prefer Ctrl to be used for functions that will open a dialog of some
      sort, though..)

TODO: Only show scrollbars if the form is actually scrollable. (This would make
      context menus look better.)

TODO: "Play" (now), in the context menu, should act like a queue-up-next, not a
      queue-at-end. (Done!)

TODO: Make the queue code more sane.
      (Done!)

TODO: Figure out when the "queue" context menu options should immediately play
      the track. Currently, they don't ever initiate playing (besides the
      "Play now" option).

TODO: A "remove from queue" option for tracks and groups, which removes them
      and their children from the queue.
      (Done!)

TODO: After the end of a shuffled queue, the next song from the group of the
      last track is played (and so on, until the group is empty). This seems
      definitely wrong.

TODO: Show a preview of where "Jump to" will go while typing.
      (Done!)

TODO: Cancelling "Jump to" should return the selected index to whatever it was
      before.
      (Done!)

TODO: Entering more than one key "at once" into a text input element will only
      move the cursor right by one character, not by the length of the inputted
      text. (This is an issue when pasting or spamming the keyboard.) Should be
      fixed in tui-lib.
      (Done!)

TODO: Pressing space while an "Up (to <group>)" button is selected both
      activates the button and pauses music (because the app detects that the
      space key is pressed). This is definitely wrong (it should do one or the
      other - I'm not too sure which, yet, but probably the latter). (Done!)

TODO: If a track's file is a symlink, the "From:" label should show where it
      links to.

TODO: The "Up (to <group>)" and "(This group has no items)" elements are not
      quite buttons nor grouplike items. They should be more consistent with
      actual grouplike items (i.e. same behavior and appearance), and should
      be less buggy. (Done!)

TODO: "Distribute" options in play/queue menu -- "don't distribute", "spread
      (across queue?) evenly", "spread randomly". (Done!)

TODO: Investigate how to make "distribute" options work better when the
      currently-playing song is contained in the group to be distributed.

TODO: The "distribute" options shouldn't show up when you've only got a track
      selected! But imagine you already had a "distribute" option selected when
      you open up the menu on a track. Is there a way to not mutate the index
      of the whereControl in that case (until the user changes the option)?
      Like the DS home screen.
